1. Field of the Invention
The present invention relates to a thermoelectric conversion element, which has a thermoelectric conversion layer consisting of an organic material and has an excellent thermoelectric conversion performance, and a thermoelectric conversion module using the thermoelectric conversion element.
2. Description of the Related Art
Thermoelectric conversion materials that enable the interconversion of heat energy and electric energy are used in a thermoelectric conversion element such as a power generating element generating power from heat or a Peltier element.
The thermoelectric conversion element can directly convert heat energy into electric power and has an advantage of not requiring a moving part. Therefore, by providing a thermoelectric conversion module (power generating device), which is obtained by connecting a plurality of thermoelectric conversion elements, in a heat exhaust site such as an incinerator or various factory facilities, it is possible to obtain electric power in a simple manner without needing to incur operational costs.
Regarding the aforementioned thermoelectric conversion element, as a thermoelectric conversion element using an inorganic material as a thermoelectric conversion material, a so-called π-type thermoelectric conversion element described in JP3981738B is known.
The π-type thermoelectric conversion element has a constitution in which a pair of electrodes separating from each other are provided, an n-type thermoelectric conversion material and a p-type thermoelectric conversion material that also separate from each other are provided on one of the electrodes and the other respectively, and the upper surfaces of the two thermoelectric conversion materials are connected to each other through the electrodes.
By arranging a plurality of thermoelectric conversion elements such that the n-type thermoelectric conversion material and the p-type thermoelectric conversion material are alternately disposed and connecting lower electrodes of the thermoelectric conversion materials in series, a thermoelectric conversion module is formed.
For example, Material Stage Vol. 1, No. 10, 2002, pp. 32 to 36 describes a thermoelectric conversion module (thermopile) obtained by connecting π-type thermoelectric conversion elements using a conductive polymer polyaniline which is a p-type thermoelectric conversion material and Pt which is an n-type thermoelectric conversion material.
A general thermoelectric conversion element including the π-type thermoelectric conversion element is constituted with an electrode on a plate-like substrate, a thermoelectric conversion layer (power generating layer) on the electrode, and a plate-like electrode on the thermoelectric conversion layer.
That is, in a general thermoelectric conversion element, the thermoelectric conversion layer is interposed between the electrodes in a thickness direction, and a temperature difference is caused in the thickness direction of the thermoelectric conversion layer, thereby converting heat energy into electric energy.
In contrast, JP3981738B describes a thermoelectric conversion element using a substrate having a high thermal conduction portion and a low thermal conduction portion, in which heat energy is converted into electric energy by causing a temperature difference in a plane direction of a thermoelectric conversion layer, not in the thickness direction of the thermoelectric conversion layer.
Specifically, JP3981738B describes a thermoelectric conversion element having a constitution in which a flexible film substrate constituted with two kinds of material having different thermal conductivities are disposed on both surfaces of a thermoelectric conversion layer formed of a P-type material and an N-type material, and the materials having different thermal conductivities are positioned on the outer surface of the substrates in a direction opposite to a direction along which electricity is conducted.